When a Mac sleeps, it sleeps, ignoring everything else

I don't know if this is an issue with Mavericks. In the past, I can leave my Mac when it's doing something, like ripping a disc, processing some photos, etc. However, I have noticed now that when my I come back and wake up my Mac, whatever stuff I was left it to do was still in progress. Eg. I was setting Lightroom to generate smart previews on a lot of photos, so it would take a while. I left my Mac overnight, thinking everything would be done by the morning. When I came the next day, waking up my sleeping Mac, it apparently went to sleep even when Lightroom was in the middle of doing its thing, and Lightroom simply continued doing things where it left off. Defeats the point of leaving my Mac overnight.

Same thing I noticed in ripping a CD. When I woke up my Mac, the CD has not yet finished being ripped.

Seriously, when Apple changed OS X from cat's names to Mavericks, I didn't expect it to also inherit the layback attitude of surfers (no offense to surfers). Sure, I can disable my Mac form going into standby, but that kinda defeats the whole automatic power saving deal, no?